Newly added attributes (by admin) don’t get saved

Hello,

When I create a new product and add the new attributes, once I click “Save Attributes”, they don’t get saved and the list remains empty.

Steps:
Products (WooCommerce) -> Add New
In the middle of the page, there is the Product menu
Product Data -> select “Variable product”
Select Attributes
There is a drop-down list with all the attributes that I defined previously (for example, Size, Color, etc.)
I select one of them, click “Add”. Then put the checkmark next to “Used for Variations”
Then if I click “Save Attributed”, there is the “round saving cursor” icon. Once it’s gone, that list is empty again.
If I disable your plugin (Product Variations Swatches), then everything works well (and that drop-in list actually becomes a white box with options I can add to it)…

Should I give you access to check it out?

Thank you,
Alexander